Method of treating and handling molten metal

ABSTRACT

A PROCESS IS PROVIDED FO PRODUCING A CASTING METAL METALS IN WHICH INGOTS ARE CAST ONE AFTER ANOTHER IN CHRONOLOGICAL SEQUENCE AT EQUALLY SPACED TIME INTERVALS CORRESPONDING TO THE INDIVIDUAL CYCLIC TIMES FOR THE NEXT SUCCEEDING PROCESSING STEPS SUCH, AS ROLLING, FORFOING OR THE LIKE.

United States Patent US. Cl. 75-93 R 9 Claims ABSTRACT OF THE DISCLOSURE A process is provided for producing and casting metal melts in which ingots are cast one after another in chronological sequence at equally spaced time intervals corresponding to the individual cycle times for the next succeeding processing step such as rolling, forging or the like.

This invention relates to metal casting and particularly to a process of producing and casting metal melts, such as steel melts, from which are cast ingots intended for subsequent processing.

Metal melts are usually produced in smelting furnaces in which they are refined to a predetermined purity and quality and, if required, alloyed. The finished melt is then poured into a ladle in which the melt is allowed to cool, since the optimum casting temperatures are substantially lower than the processing temperatures of the melt. When casting ingots which are subsequently to be rolled for example, and when the casting temperature is attained, the entire charge is teemed into an appropriate number of ingot molds in which it is cooled. The solidified ingots are then placed into a soaking furnace from which they are taken for further processing in conformity with the operating cycle time of the rolling mill. Such a method requires a considerable expenditure on apparatus and is not suitable when casting extremely long ingots in accordance with the method described in German patent application No. P 19 31 715.8, since, during the subsequent processing of such ingots, it is possible to dispense with heat treatment in the soaking furnace and to further process the ingots directly by using the casting heat.

A feature of the invention is to provide a process by which the producing and casting of melts, particularly for producing ingots, can be synchronized with the further processing of the ingots while at the same time maintaining the most economical manufacturing conditions.

In accordance with the invention, the ingots are cast one after the other in a chronological sequence corresponding to the cycle time of the further processing of the ingots.

However, such a process will be economical only if the melt is to be produced and treated simultaneously for a large number of ingots. If a continuous process in accordance with the invention is used, in which individual ingot quantities are cast in a timed chronological sequence, the optimum casting temperatures can be maintained for only a relatively short time using conventional methods. If the intervals between the cycles were increased, the last ingot quantities removed would no longer have the desired casting properties. On the other hand, the cooling of the melt to the prescribed casting temperature would take a very long time in the ladles, which are usually well insulated, and the relatively long interval of time between pouring the melt into the ladle and attaining favorable casting temperatures would not be compatible with a continuous sequence of working processes.

Thus, a casting cycle in a casting process in accordance with the invention includes the following steps:

(a) a metal charge is processed in a smelting furnace to form a melt of predetermined quality;

(b) after treatment in the smelting furnace, the melt is transferred to a heatable, metallurgical vessel and the smelting furnace is then freshly charged;

(0) the melt in the metallurgical vessel is maintained at casting temperature and portions of the melt are removed from the metallurgical vessel at predetermined intervals and cast into ingots; and

(d) after the last portion to be cast has been removed, a residual melt is left in the metallurgical vessel for mixture with the next melt to be placed into the vessel from the smelting furnace.

Thus, by way of adaptation, with respect to time, to the further processing of the ingots, the portions of melt required for casting the ingots can be made available with consistent casting properties at predetermined instants, so that, after solidifying, the ingots cast therefrom may be fed in a specific chronological sequence for further processing by utilizing the casting heat.

In order to bring the melt, introduced into the metallurgical vessel from the smelting furnace, to casting temperature as soon as possible, the heating of the metallurgical vessel can be interrupted or substantially limited after the last portion to be cast has been removed and while the residual melt and the freshly introduced melt are cooled. If required, the melt may also be subjected to any desired secondary treatment in the metallurgical vessel.

When the melt is taken from the metallurgical vessel at uniform intervals of time, the charge time of the metal in the smelting furnace preferably corresponds to no more than the time required between introducing the melt into the metallurgical vessel and the last sequential casting operation, in order to match the charge time of the metal to the sequential removal of the ingot quantities of melt from the metallurgical vessel.

If secondary treatment of the melt is to be effected in the metallurgical vessel, the secondary treatment time corresponds advantageously to no more than one interval of time in the sequence of individual casting operations in which the melt is taken from the metallurgical vessel, so that the casting cycle is not interrupted by the secondary treatment.

If the charge time when producing the melts has to be longer than the sum of the casting intervals, there may be provided two or more smelting furnaces which feed thelmelt to the metallurgical vessel in an appropriate cyc e.

Conversely, if the sum of the casting intervals in one casting cycle substantially exceeds the charge time, there may be provided two or more metallurgical vessels which are filled directly one after the other with a charge from the smelting furnace after the melt has been prepared in the smelting furnace.

The invention is further described, by way of example, with reference to a preferred embodiment.

Any optional rolling mill installation or forging plant, to which ingots are to be supplied at uniform intervals of time of, for example, 15 minutes, is connected at the output side of a steel smelting and casting apparatus by which the process of the invention may be carried out. The smelting apparatus comprises an electric furnace n which a melt may be produced simultaneously for four ingots for example. A heatable metallurgical vessel comprising a crucible induction furnace is connected on the output side of the electric furnace. The induction furnace has a capacity somewhat greater than the capacity of the electric furnace, and can accommodate the melt for five ingots for example.

The melt is maintained at an optimum casting temperature in the crucible induction furnace, and, corresponding to the predetermined working cycle time for the subsequent processing of the individual ingots, one ingot is cast every 15 minutes by taking one ingot quantity of melt from the induction furnace. After solidifying, the ingot is removed from the mold and passed through a soaking furnace and then fed directly to the rolling mill or the forging plant. The casting cycle is completed after four ingots have been cast and a quantity of melt for about one ingot is still located in the induction furnace. The next casting cycle is then commenced by introducing a fresh charge into the induction furnace from the electric furnace. The fresh charge corresponds to about four times the quantity of melt required for one ingot. The fresh charge mixes with the cooler residual melt which thus accelerates the drop in temperature, so that the optimum casting temperature is attained no later than the expiry of the ingot processing cycle time of 15 minutes.

The electric furnace is recharged immediately after it has been emptied, and the charge time must not be longer than one casting cycle which comprises four casting operations and equals four ingot processing cycles, Le. 60 minutes. After the expiry of four ingot processing cycles during which four ingots have been cast, the melt freshly produced in the electric furnace during the four cycles is transferred into the induction furnace and mixed with the residual melt.

By this process, one ingot can be produced every 15 minutes in a continuous time sequence under the same casting conditions and can be subjected to a further non-cutting process immediately afterwards by utilizing the casting heat.

If the plant is to be shut down, five ingots are cast from the crucible induction furnace during the last casting cycle, at the same time maintaining the sequence of ingot processing cycles, so that the induction furnace is subsequently completely emptied.

When the plant is first put into operation, the electric furnace is charged with a quantity from which five ingots can be produced, the entire melt being fed to the crucible induction furnace when the latter is charged for the first time.

If the capacity of the smelting furnace is too small to accommodate the melt for five ingots, a quantity for four ingots can be introduced during the first charge and during the subsequent charges, only three ingots being cast from the crucible induction furnace during the first casting cycle, whereby the residual quantity remains in the induction furnace in order to be mixed with the freshly introduced melt for the second casting cycle which com prises four casting operations.

In the foregoing specification, I have set out certain preferred embodiments and practices of my invention, however, it will be understood that this invention may be otherwise embodied within the scope of the following claims.

I claim:

1. A process for producing and casting metal melts which includes a plurality of successive casting cycles, 60

each of which comprises the steps of (a) transferring substantially all of a treated metal melt of predetermined character from a smelting furnace to a heatable, metallurgical vessel;

4 (b) maintaining the melt in the metallurgical vessel at casting temperature and, while so maintaining the melt at casting temperature, removing the melt in ingot portions at predetermined intervals of time; 5 (c) re-charging the smelting furnace and treating the charge in the furnace to form a treated metal melt for a subsequent casting cycle during the performance of step (b) above; and (d) retaining a residual portion of the melt in the metallurgical vessel substantially equivalent to one ingot portion after the last ingot portion to be cast has been removed for mixture with the next melt to be transferred to the metallurgical vessel at the commencement of the next casting cycle. 2. A process as claimed in claim 1, in which the metallurgical vessel is heated during most of the casting cycle but such heating is interrupted or substantially reduced after the last ingot portion to be cast has been removed.

3. A process as claimed in claim 1, in which the melt in the metallurgical vessel is subjected to secondary treatment before the removal of the first ingot quantity therefrom.

4. A process as claimed in claim 3, in which the duration of said secondary treatment effected in the metallurgical vessel is no longer than one time interval between successive removals of ingot portions of the melt from the metallurgical vessel.

5. A process as claimed in claim 1, in which the duration of the charging of the smelting furnace and the treatment of the melt therein is no longer than the time required for introducing the melt into the metallurgical vessel and removal of all ingot melts therefrom in one casting cycle.

6. A process as claimed in claim 1, in which treated metal melts from at least two parallel operating smelting furnaces are transferred alternately to the metallurgical vessel.

7. A process as claimed in claim 1, in which the treated metal melt is transferred from the smelting furnace to at least two parallel operating metallurgical vessels.

8. A process as claimed in claim 1 wherein the retained residual portion is substantially equal to an ingot portion.

9. A process as claimed in claim 1 wherein the metallurgical vessel is provided with suflicient metal for five ingot portions, and is recharged after each four ingot portions are removed whereby at least one ingot portion is retained as a residual therein.

References Cited UNITED STATES PATENTS 5/1970 Harrill et al 266-38 9/1967 Luna 266-38 9/1970 Werner 266-38 7/1956 Carleton 164-155 4/1968 Boitchenko et a1. 164155 4/1969 Sommer 164-155 X CHARLES W. LANHAM, Primary Examiner D. C. REILEY (HI, Assistant Examiner U.S. Cl. X.R.

29-Dig. 5; 164-155, 266; 266-38 

